System for lining a section of a wellbore

ABSTRACT

A system for lining a section of a wellbore with an expandable tubular element is provided. The system includes an elongate string extending into the wellbore, the string being provided with the tubular element in the unexpanded form thereof whereby the tubular element surrounds a lower portion of the string. The string is further provided with an expander arranged at a lower end part of the tubular element and anchoring means for anchoring an upper end part of the tubular element in the wellbore.

FIELD OF THE INVENTION

The present invention relates to a system for lining a section of awellbore with an expandable tubular element, whereby an elongate stringextends into the wellbore. An example of such string is a drill stringused to drill wellbore.

BACKGROUND OF THE INVENTION

During conventional wellbore drilling sections of the wellbore aredrilled and provided with a casing or a liner in subsequent steps. Ineach step, the drill string is lowered through the casings alreadyinstalled in the wellbore, and a new section is drilled below theinstalled casings. By virtue of this procedure, casing which is to beinstalled in the newly drilled section has to pass through earlierinstalled casing, therefore the new casing must be of smaller outerdiameter than the inner diameter of the earlier installed casing. As aresult the available diameter of the wellbore becomes smaller withdepth. For deep wells, this consequence can lead to impractically smalldiameters.

In the description below, references to “casing” and “liner” are madewithout an implied difference between such types of tubulars. Similarly,references to “lining” can be understood to mean: providing a liner or acasing in the wellbore.

It has been proposed to overcome the problem of stepwise smaller innerdiameters of wellbore casing by installing a tubular element in awellbore and thereafter radially expanding the tubular element to alarger diameter by means of an expander which is pulled, pushed orpumped through the tubular element. However, such method requires thatthe drill string is to be removed from the wellbore each time a newexpandable tubular element is installed in the wellbore.

SUMMARY OF THE INVENTION

In accordance with the invention there is provided a system for lining asection of a wellbore with an expandable tubular element, comprising anelongate string extending into the wellbore, said string being providedwith the tubular element in the unexpanded form thereof whereby thetubular element surrounds a lower portion of the string, the stringfurther being provided with an expander arranged at a lower end part ofthe tubular element and anchoring means for anchoring an upper end partof the tubular element in the wellbore.

In use the expandable tubular element (e.g. a liner or a casing section)is initially supported on the drill string, and at the desired depthexpanded against the borehole wall for its permanent installation in thewellbore by first anchoring the upper end part against the inside of theexisting casing, wellbore wall or other tubular element, and thenpulling the expander upwards through the tubular element. Thereafter thedrill string can be retrieved to surface completely. By this method thedrill string with the expandable tubular element thereon can be operatedto drill the wellbore like is normally done when drilling wells in theground without having less strength. In the unexpanded state of theexpandable tubular element the entire drill string can be pulled tosurface to exchange worn parts, should this become necessary. The methodcan be repeated to drill another new hole section below the previouslyexpanded tubular element. The expanded element may be additionallysealed inside the borehole by pumping a hardening fluid into anyremaining annular space between the expanded element and the boreholewall.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be described hereinafter in more detail and by way ofexample with reference to the accompanying drawings in which:

FIG. 1 schematically shows a longitudinal view, partly in section, of anembodiment of the system of the invention;

FIG. 2A schematically shows a longitudinal section of an expanderapplied in the embodiment of FIG. 1, when secured to the lower end ofthe string;

FIG. 2B schematically shows a longitudinal section of the expander ofFIG. 2B when released from the string;

FIG. 3A schematically shows a longitudinal section of an anchoringsystem applied in the embodiment of FIG. 1, before activation thereof;

FIG. 3B schematically shows a longitudinal section of the anchoringsystem of FIG. 3B during an initial stage of activation thereof;

FIG. 3C schematically shows a longitudinal section of the anchoringsystem of FIG. 3B during a subsequent stage of activation thereof;

FIG. 4 schematically shows section 4—4 of FIG. 3A;

FIG. 5 schematically shows section 5—5 of FIG. 3B; and

FIG. 6 schematically shows a detail of the expander of FIGS. 2A and 2B.

For the purpose of simplicity, in FIGS. 2A, 2B, 3A, 3B is shown only onehalf of the respective longitudinal section, the other half beingsymmetrical thereto with respect to the longitudinal axis (indicated byreference numeral 5).

In the Figures, like reference numerals relate to like components.

DESCRIPTION OF THE EMBODIMENT

In FIG. 1 is shown a tubular drill string 1 extending into a wellbore 2formed in an earth formation 3. An upper section of the wellbore 2 isprovided with a casing string 4 having longitudinal axis 5. A newlydrilled open hole section 6 which has not yet been provided with casingextends below the casing string 4. The drill string 1 includes aplurality of jointed drill string sections 8 (e.g. sections of drillpipe) and has a lower portion 10 around which an expandable tubularliner 12 is substantially concentrically arranged. A lower end part ofthe drill string 1, i.e. below the liner 12; is formed by a bottom holeassembly (BHA) 14 which includes a drill bit 16 of bi-centred oreccentric type, a drilling motor 18 for driving the drill bit 16, and ameasurement while drilling tool (MWD) 20 to aid in the process ofdirectional drilling of the wellpath to a particular subsurfacelocation. On top of the MWD tool 20 other components which are normallyused in drilling of wells can be included. A characteristic of thebi-centred drill bit 16 is that it drills borehole sections of a largerdiameter than its own diameter as the bit, when rotated, describes alarger circular area than when not rotated. The drill string 1 isfurther provided with an expansion cone 22 arranged on top of the BHA10, for expanding the liner 12 through plastic deformation by moving theexpansion cone 22 through liner 12. The lower portion 10 of the drillstring 1 includes an axial extension sub 23 which allows the drillstring 1 to slide a short distance axially relative to the liner 12 inorder to compensate for differential thermal expansion of the drillstring 1 and the liner 12.

Referring further to FIGS. 2A and 2B, the expansion cone 22 is providedwith releasable support means for supporting the liner 12, which supportmeans includes a plurality of retractable holding blocks 24circumferentially spaced along the outer surface of the cone 22 andpositioned in respective holes 26 arranged in the conical outer surfaceof the expansion cone 22. The holding blocks 24 form with their combinedoutside surfaces a thread pattern 28 like a buttress thread, whichthread pattern engages with a complementary buttress like thread pattern30 on the bottom end of the liner 12. Engagement of the thread pattern28 with the thread pattern 30 is accomplished by sliding the lower endof the liner 12 with the thread pattern 30 over the thread pattern 28 ofthe retractable holding blocks 24. In the process of engagement theliner 12 can only move downwards and not upwards. The lower end of theliner 12 can alternatively be screwed onto the holding blocks 24,whereby the preferred threading direction is counter clockwise. Aprotection sleeve 32 is attached to the lower end of the liner 12 toprevent damage to the outer surface of the expansion cone 22.

The expansion cone 22 is at its inner surface provided with a ring 34arranged in an annular recess 36 of the cone 22 in a manner that thering is axially slideable in the annular recess 36. As is evident fromFIGS. 2A, 2B, the holes 26 are in fluid communication with the annularrecess 36, and the ring 34 and the holding blocks co-operate in a mannerthat downward sliding of the ring causes radial retraction of theholding blocks 24. The ring has a landing profile 38 which matches aclosing plug 40 (shown in FIGS. 1, 3A, 3B) which can be pumped throughthe drill string 1. When the closing plug 40 seats on the landingprofile 38, the fluid circulating passage through the drill string 1 isblocked. Continued pumping of fluid through the string 1 causes thefluid pressure above the closing plug 40 to rise and thereby to slidethe ring 34 downwards. As a result the holding blocks 24 are allowed toretract radially inward so that thereby the expansion cone 22 isreleased from the liner 12.

Referring is further made to FIGS. 3A and 3B. The drill string 1includes an expansion device 42 arranged at the upper end of the liner12, for radially expanding the liner 12 against the casing 4 so as toform a firm connection and fluid seal with the casing 4. The expansiondevice 42 includes respective upper and lower tubular members 44, 46which are axially movable relative to each other by virtue of a splinearrangement 48 capable of transmitting torque between the members 44,46. Small clearances between the splines of the two members 44, 46define a plurality of small longitudinal fluid passages 49 of which someare in fluid communication with the interior 50 of the drill string 1via openings 52 provided in the lower member 46. The outer surface ofthe lower member 46 is sealed against the inner surface of the uppermember 44 by annular seals 54 arranged above the openings 52. The lowermember 46 is sealed against the liner 12 by annular seals 56.

The two members 44, 46 are locked to each other by a locking ring 58which is arranged in an annular recess 60 of the lower member 46, andwhich extends into an annular recess 62 of the upper member 44 so as totransmit axial loads between the two members 44,46. The locking ring 58is spring loaded so as to retract fully into the annular recess 60 whenreleased. A split seating ring 64 is arranged in the lower member 46 atthe level of the annular recess 60 so as to close-off the recess 60, theseat ring 64 being axially slideable relative to lower member 46. Theportion of the recess 60 between the seat ring 64 and the locking ring58 is filled wit an incompressible fluid. A stop ring 65 is fixedlyconnected to the inner surface of the lower member 46, a suitabledistance below the annular recess 60.

Referring further to FIGS. 4 and 5, the upper member 44 is provided withan expandable ring-shaped mandrel 66 which is circumferentially dividedinto a plurality of mandrel segments 68 so as to allow the mandrel 66 tobe operable between a radially retracted mode (as shown in FIG. 4) inwhich adjacent segments are in abutment, and a radially expanded mode(as shown in FIG. 5) in which adjacent segments are circumferentiallyseparated from each other. The mandrel 66 has a lower surface 70 (FIG.3A, 3B) which tapers downwardly in radial outward direction, and anupper surface 71 which tapers upwardly in radial outward direction. Thelower surface 70 is arranged in contact with a complementaryfrustoconical surface 72 of a first annular actuator 74 which forms anintegral part of the upper member 44. The upper surface 71 is arrangedin contact with a complementary frustoconical surface 76 of a secondannular actuator 78 which is pushed against the mandrel by a springdevice 80. By this arrangement the mandrel 66 is moved to its radiallyexpanded mode when the upper member 44 moves upwardly relative the lowermember 46. A fluid chamber 82 is formed between the first actuator 74and the lower member 46, which chamber 82 is in fluid communication withthe interior 50 of the drill string 1 via the small fluid passages 49and the openings 52. Thus, when drilling fluid is pumped from theinterior 50 of the drill string 1 via openings 52 and fluid passages 49,into the fluid chamber 82, the upper member 44 is induced to moveupwardly relative the lower member 46. The mandrel 66 has a radial outersurface of a similar quality to the outer surface of the expansion cone22. The segments 68 are interconnected by linking elements 84 (FIG. 5)which also serve to cover the gaps formed between the segments 68 asthese move radially outwards. The gaps can also be covered by selectedintermeshing profiles of the segments 68.

During normal operation the new open hole section 6 is drilled belowcasing 4, whereby the drill string 1 is lowered through the casing 4.The bi-centred drill bit 16 drills the new borehole section 6 to adiameter which is about equal to the diameter of the upper boreholesection 2. During drilling a stream of drilling fluid is pumped throughthe interior passage 50 of the drill string 1. After section 6 has beendrilled, the drill string 1 is positioned such that an upper end portionof the liner 12 is located inside the casing 4. Subsequently the closingplug 40 is pumped together with the stream of drilling fluid into thedrill string 1 until the plug 40 becomes seated on the seating ring 64.Thereby the closing plug 40 blocks the fluid passage 50, and continuedpumping of fluid into the drill string 1 causes the seat ring 64 toslide downwards against the stop ring 65. Through this movement theopenings 52 become unsealed and the uncompressible medium is pushed outby the locking ring 58 which fully retracts into the annular recess 60.Thus, the upper member 44 becomes unlocked from the lower member 46.

Drilling fluid which enters the fluid chamber 82 via openings 52 andfluid passages 49 causes the fluid chamber 82 to act as a hydraulicpiston/cylinder assembly whereby the upper member 44 is pushed upwardlyrelatively the lower member 46. The mandrel 66 is thereby subjected toan upward force at its lower tapering surface 72 from the upper member44, and to a downward reaction force at its upper tapering surface 71from spring device 80. As a result the mandrel segments 68 are pushedradially outward so that the mandrel 66 moves to its radially expandedmode (FIG. 3B) whereby the upper end part of the liner 12 plasticallydeforms and becomes radially expanded against the casing 4. Then theupper member 44 continues to being pushed upwards thereby expanding theremaining upper end of the liner 12 (FIG. 3C). When the upper end of theliner 12 is fully expanded against the existing casing 4, the uppermember 44 reaches a stop (not shown) to limit further travel. As aresult the upper end of the liner 12 becomes firmly anchored against thecasing 4.

Next, the closing plug 40 is released from the seating ring 64 byapplying increased pumping pressure so that stop ring 65 breaks and theseating ring 64 is allowed to slide further downwards into an axialposition where it can expand to a larger diameter. The closing plug 40is pumped further down the drill string 1 until it seats on landingprofile 38 of ring 34. Continued pumping of drilling fluid through thedrill string 1 causes the ring 34 to slide downwards in annular recess36, and thereby causes the holding blocks 24 to radially retract. Inthis manner the expansion cone 22 becomes released from the liner 12.

In a next step the drill string 1 with the expansion cone 22 is pulledupwards through the liner 12 whereby the liner 12 is restrained againstaxial movement by virtue of its anchored upper end part. By pulling theexpansion cone 22 through the liner 12, the liner 12 is expanded to anouter diameter almost equal to the diameter of the wellbore 2.

The wall thickness of the upper end of liner 12 can be different,especially smaller, from the wall thickness of the remainder of theliner 12 to reduce the force required to expand the liner.

Instead of a bi-centred drill bit, an underreamer or an expandable bitcan be used.

The expandable tubular liner can have a predetermined length which islonger than the initially planned newly drilled hole section such thatthere is an overlap with the existing casing. The expandable liner canbe installed at any other intermediate depth should this becomenecessary.

The expandable liner may contain preformed holes which are closed in theunexpanded stage and which open up during expansion to allow pumping ofa hardening fluid into the annular space between the expanded liner andthe borehole wall.

Instead of applying the spring device 80 to provide a downward reactionforce to the second annular actuator 78 in response to upward movementof the upper member 44 against the mandrel 66, a hydraulicpiston/cylinder assembly can be applied to provide a downward reactionforce to the second annular actuator 78. Such piston/cylinder assemblyis suitably powered by hydraulic fluid pressure from fluid present inthe interior 50 of the drill string 1.

While the illustrative embodiments of the invention have been describedwith particularity, it will be understood that various othermodifications will be readily apparent to, and can be easily made by oneskilled in the art without departing from the spirit of the invention.Accordingly, it is not intended that the scope of the following claimsbe limited to the examples and descriptions set forth herein but ratherthat the claims be construed as encompassing all features which would betreated as equivalents thereof by those skilled in the art to which thisinvention pertains.

1. A system for lining a section of a wellbore with an expandabletubular element, comprising an elongate string extending into thewellbore, said string being provided with the tubular element in theunexpanded form thereof whereby the tubular element surrounds a lowerportion of the string, the string further being provided with anexpander arranged at a lower end part of the tubular element and anchorfor anchoring an upper end part of the tubular element in the wellbore,wherein said upper end part of the tubular element extends into an outertubular element arranged in the wellbore and surrounding said upper endpart, and wherein the anchor includes radial expansion means forradially expanding the upper end part of the tubular element against theouter tubular element.
 2. The system of claim 1, wherein the tubularelement is supported by the string by a releasable support.
 3. Thesystem of claim 2, wherein the releasable support comprises at least oneholding device provided to the string, each holding device being movablebetween a radially retracted mode in which the string is axially movablerelative to the tubular element and a radially extended mode in whichthe holding device supports the tubular element.
 4. The system of claim3, wherein the string is provided with a longitudinal fluid passage forwellbore fluid and an annular seat arranged in the fluid passage, saidannular seat being axially movable relative to the string and beingoperable so as to move each holding device from the extended mode to theretracted mode thereof upon the seat being axially moved by a plugpumped through the fluid passage.
 5. The system of claim 4, wherein saidfluid passage continues through the expander, and wherein each holdingdevice is arranged at the level of the expander.
 6. The system of claim5, wherein the outer tubular element is one of a wellbore casing, awellbore liner and a tubular patch.
 7. The system of claim 1, whereinthe radial expansion means comprises a mandrel formed of a plurality ofradially movable mandrel segments.
 8. The system of claim 7, wherein themandrel is arranged to be radially expanded by a hydraulic activatingsystem.
 9. The system of claim 4, wherein, the radial expansion meanscomprises a mandrel formed of a plurality of radially movable mandrelsegments and the mandrel is arranged to be radially expanded by ahydraulic activating system, and the hydraulic activating systemcomprises a fluid chamber in fluid communication with said longitudinalfluid passage during radial expansion of the mandrel.
 10. The system ofclaim 1, wherein said string is a drill string for drilling thewellbore.
 11. A method of lining a section of a wellbore with anexpandable tubular element, comprising: drilling a section of thewellbore using a drill string; anchoring the upper part of theexpandable tubular element in the wellbore using an anchoring means;releasing the drill string from the expandable tubular element; andpulling an expander by means of the drill string through the expandabletubular element so as to radially expand the expandable tubular element.